Abortion clinics nationwide face significant threats of harassment, intimidation, and violence, according to a new report showing that threats of violence against abortion providers have doubled since 2010.

The survey of 242 abortion providers in the United States found that there has been significantly higher levels of threats and targeted intimidation of doctors and staff in recent years. The report comes as widespread intimidation tactics were deployed against clinics during the anniversary of Roe v. Wade, the Supreme Court’s 1973 decision affirming a woman’s right to choose an abortion.

More than 500 plastic handcuffs placed inside “care packages” were reportedly delivered to abortion clinics throughout the country last week, according to The Christian Post. The packages were sent by the anti-choice organization Pro-Life Action League.

The packages included a postcard mentioning the recent arrest of Naresh Patel, an Oklahoma physician, and the ominous handwritten message: “Could you be next?”

Patel was arrested in December and charged with racketeering and three counts of obtaining money by false pretenses, according to reporting by the Oklahoman. An undercover investigation found that Patel was providing abortion-inducing drugs to patients without verifying that they were pregnant.

The message was written by Eric Scheidler, executive director of the Pro-Life Action League. “I thought this could really be a strong message to abortionists who really think seriously about the business that they’re involved in,” Scheidler told The Christian Post.

Pro-Life Action League received assistance in mailing the packages from the radical anti-choice organization Operation Rescue, whose members identified the clinics across the country that received the packages.

The use of similar intimidation techniques is on the rise, according to the National Clinic Violence Survey, conducted by the Feminist Majority Foundation. The report is the first comprehensive nationwide survey of violence at women’s health clinics since 2010.

The survey found that nearly one in five clinics experienced severe violence. Severe types of anti-choice violence affected 19.7 percent of clinics nationwide, down from the 23.5 percent of clinics nationwide that reported experiencing severe violence in 2010.

Incidents of wanted-style posters of abortion providers, pamphlets targeting doctors and clinic staff, and harmful information and pictures of doctors posted on the Internet have all significantly increased over the past four years, according to the report. The posters and flyers often include phrases like “Killers Among Us,” “Wanted For Killing,” and “Stop This Abortionist Now.”

The rate of clinics reporting stalking of physicians has also increased, from 6.4 percent of clinics in 2010 to 8.7 percent in 2014.

“The most stunning result in the survey, really, is this surge in serious threats that are being carried out against providers nationwide,” duVergne Gaines, the director of the National Clinic Access Project and one of the authors of the report, told ThinkProgress. “Those threats have almost doubled since 2010.”

The survey findings mirror reports by clinic staff and escorts from around the country who said they have seen an increase in clinic harassment. Other examples of anti-choice harassment, intimidation, and even acts of vandalism against abortion clinics have been reported around the country over the past year.

Abortion clinic physicians, staff, and escorts in Louisiana faced a barrage of harassment from anti-choice activists during July. Hundreds of activists with Operation Save America (OSA) descended on New Orleans to stage a week of protests throughout the city.

The activists targeted reproductive health-care clinics, personal residences, and even houses of worship in the hopes of intimidating abortion providers and reproductive rights supporters.

OSA activists were at the headquarters of the Jackson, Mississippi, police department a week after the protest in New Orleans, while fellow activists were facing criminal charges associated with protest activities outside the Jackson Women’s Health Organization. Three of the four activists were found guilty of charges including obstructing the sidewalk entrance to the clinic.

All Families Healthcare, a family medicine and reproductive health-care facility in Kalispell, Montana, was broken into and severely vandalized in March. The man who allegedly vandalized the facility is the son of a former board member of the local anti-choice crisis pregnancy center.

Susan Cahill, a physician assistant who manages the Kalispell office, told Rewire at the time that she believed the break-in was part of a coordinated effort to intimidate the facility into no longer providing abortion care. Cahill has been forced to close the facility indefinitely, while the suspect stands charged with four felonies, including burglary, criminal mischief, theft, and attempted burglary.

Increases in the incidents of harassment of abortion clinics appear to coincide with the increasing amount of legislation passed to restrict access to reproductive health care. Lawmakers across the country have returned to state houses this month and have renewed their legislative assault on women’s rights.